In various embodiments, the beam parameter product and/or beam shape of a laser beam is adjusted by directing the laser beam across a path along the input end of a cellular-core optical fiber. The beam emitted at the output end of the cellular-core optical fiber may be utilized to process a workpiece.

An optical fiber for converting a Gaussian laser beam into a Bessel laser beam may include a first segment optically coupled to a second segment with a transition region, the first segment having a first outer diameter greater than a second outer diameter of the second segment. The first segment may include a first core portion with a first cladding portion extending around the first core portion. The first core portion may have an annular core region with a relative refractive index relative to the first cladding portion. The second segment may include a second core portion with a second cladding portion extending around the second core portion. The second core portion has a relative refractive index relative to the second cladding portion and the relative refractive index of the first annular core region may be substantially equal to the relative refractive index of the second core portion.

An amplification optical fiber according to the present invention includes: a core doped with an active element, through which multi-mode light propagates; an inner cladding that surrounds the core and has a refractive index lower than that of the core; and an outer cladding that surrounds the inner cladding and has a refractive index lower than that of the inner cladding. The inner cladding has a polygonal outline in a cross section perpendicular to the longitudinal direction, and the inner cladding has a permanent twist applied by turning around the central axis of the core.

An optical fiber device may include a unitary core including a primary section and a secondary section, wherein at least a portion of the secondary section is offset from a center of the unitary core, wherein the unitary core twists about an optical axis of the optical fiber device along a length of the optical fiber device, and wherein a refractive index of the primary section is greater than a refractive index of the secondary section; and a cladding surrounding the unitary core.

Provided is an optical device whose resin member is less likely to reach a high temperature, as compared with that of a conventional optical device. The optical device (1) includes (i) an optical fiber (11) in which a jacket-removed section (I1) is provided and (ii) a resin member (12) in which the jacket-removed section (I1) is embedded. The jacket-removed section (I1) is a section in which a part of a jacket (112) covering an outer surface of a cladding (111b) is removed so that only a part of the outer surface of the cladding (111b) is exposed in a cross section of the optical fiber (11).

A method and apparatus for imaging using a double-clad fiber is described.

Provided is an optical device whose resin member is less likely to reach a high temperature, as compared with that of a conventional optical device. The optical device (1) includes (i) an optical fiber (11) in which a jacket-removed section (I1) is provided and (ii) a resin member (12) in which the jacket-removed section (I1) is embedded. The jacket-removed section (I1) is a section in which a part of a jacket (112) covering an outer surface of a cladding (111b) is removed so that only a part of the outer surface of the cladding (111b) is exposed in a cross section of the optical fiber (11).

A high harmonic optical generator comprising a laser arrangement for emitting a beam of polarized radiation at a fundamental frequency and an optical waveguide having a hollow core for a gaseous harmonic generation medium for the generation of high harmonics of the fundamental frequency, the optical waveguide having an optical propagation axis along the hollow core, the laser arrangement is configured to couple the beam of polarized radiation along the propagation axis of the hollow core optical waveguide to provide a beam of optical driving radiation for the high harmonic generation, the optical driving radiation having a plane of polarization that rotates about the propagation axis.

Disclosed are optical beam delivery devices and methods to produce, from a single-mode input beam having a fundamental mode and an M.sup.2 beam quality of about 1.5 or less, an output beam having an adjustable spatial intensity distribution that is adjustable between near Gaussian and ring-shaped profiles, the near Gaussian profile corresponding to an M.sup.2 beam quality of about 1.5 or less. A first length of optical fiber is for adjusting the single-mode input beam to generate an adjustable beam based on controllable perturbation applied to the first length of optical fiber. A second length of optical fiber is for coupling the adjustable beam into one or both a central core confinement region and an annular higher-index confinement region. The second length of optical fiber is configured to provide at its output the output beam having the adjustable spatial intensity distribution.

Hollow core optical waveguiding enabled by zero-index materials are provided. In one embodiments, a zero-index optical fiber is provided, the zero-index optical fiber comprising: a core comprising air for propagating light; and a cladding configured to surround the core, wherein the cladding comprises a zero-index material. The zero-index material including transparent conducting oxides such as indium tin oxide.